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BP ready to water flood at Aurora Prudhoe satellite has 110 million to 146 million barrels of oil in place, 75-100 billion cubic feet of formation gas and 15-75 bcf of gas cap gas By Kristen Nelson PNA Editor-in-Chief
Prudhoe Bay field operator BP Exploration (Alaska) Inc. is ready to start water flood at the Aurora satellite on the west side of Prudhoe Bay.
BP has requested pool rules and area injection rules, and told the Alaska Oil and Gas Conservation Commission at a July 24 hearing that it wants to start water flood operations at Aurora the first week of August. The commission requested some additional information and said it would be keeping the record of the hearing open through the end of July for that information. Because the record open until the end of July, the commission told BP that it couldn’t promise a decision by the first week in August.
Aurora is in production from wells on S pad and through the end of May the field had produced more than 1 million barrels of oil and 6.5 billion cubic feet of gas.
110-146 million barrels of original oil The Aurora area was first drilled in 1969. A number of S pad wells were drilled through the Kuparuk River formation, which overlies the deeper Sadlerochit reservoirs produced at Prudhoe Bay, and in 1999, ARCO Alaska Inc. drilled the V-200 well as a Prudhoe Bay satellite prospect with both Schrader Bluff and Kuparuk formation objectives.
The Kuparuk formation oil at Aurora ranges from 25-30 degrees API gravity and there are an estimated 110-146 million barrels of original oil in place, 75-100 billion cubic feet of formation gas and 15-75 bcf of gas cap gas.
BP told the commission that there are five structurally defined areas at Aurora and five reservoir sands, two of which contain the primary concentration of resource and two of which are considered secondary.
BP said that with primary recovery — solution gas drive, gas cap expansion and aquifer support — an estimated 12 percent of the original oil in place would be recovered with a peak production rate of 7,000-9,000 barrels of oil per day. The company said that water flood is expected to produce 34 percent of the original oil in place.
Field development will require 10 to 13 producing wells and five to seven injection wells. With water flood, production is expected to peak at 14,000-17,000 bopd.
BP is also studying miscible injectant for Aurora, but told the commission that no decision has been made yet on an MI recovery.
Six development wells have been drilled and Aurora development will be from S pad and will require no new roads or facilities. Safety valves an issue There was some discussion in the hearing about subsurface safety valves. Commission Chair Cammy Taylor told BP that the commission is under fire from other agencies for a decision it made in the 1990s not to require the subsurface safety valves after a hazard risk study by North Slope operators.
The commission was told there was no change from the 1994-95 risk analysis, but Commissioner Julie Heusser asked for a copy of a recent assessment on subsurface safety valves.
Heusser also asked what type of surface safety valves BP will use at Aurora. BP said it is using electric pilots on the surface safety valves at S pad and said the electric pilots, also in use at Milne Point, have had lower failure rates than hydraulic pilots.
Participating area smaller than requested BP told the commission that the Department of Natural Resources has designated expansion areas at Aurora.
BP had requested an Aurora participating area of approximately 10,740 acres from DNR last year, but in a December decision DNR’s Division of Oil and Gas approved a participating area of only 3,920 acres, with provisions for automatic expansions as additional Aurora wells are drilled and begin producing.
In 2000, BP drilled the three Aurora reservoir development wells from S-Pad. Production from the Aurora wells began in November on a tract basis.
The division said that consistent with the practice in the Milne Point unit, it will expand the Aurora participating area as BP drills additional wells in the individual fault blocks and ties those wells into production facilities. Four expansion areas have been identified.
“The conditions for automatic expansion encourage exploration and development of the entire Aurora reservoir, rather than concentrated development in the core area,” the division said.
Subject to drilling of qualified wells within each area, four expansion areas are specified for Aurora, containing 1,280 acres, 1,040 acres, 640 acres and 1,360 acres. Qualified wells may be either producers or injectors completed in the Kuparuk formation at Aurora, and the area will be automatically expanded when the state receives required notification information for the wells.
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